أخي الكريم أبوعبدلله لك كل التحية والأحترام الموضوع كالتالي:-
Aircraft Cleaning
The first step in corrosion controle is to keep the aircraft clean .before start cleaning the aircraft you should protect spacific areas such as pitot tubes and static openings it should be always covered . do not use non aproved cleaning products because that may cause hydrogen embrittlment . When using chemical cleaning agent you should :
1-open all electrical circuits.
2-Do not use syntthetic wiping cloths with flamable agents .
3-chemical agents should not be applied with atomizing spray equipment.
4-keep all agents away from open flames.
5-Do not mix any cleaning agents with any solvent.
6-Do not use cleaning compounds at higher concentration than what is recommended .
7-All drain holes , flap valves , etc should be opened before washing .
8-Do not breath the vapor while using Ammonium Hydroxide and avoid skin contact.
9-Do not use excessive amounts of cleaning agents on controle cables .
10-Cover tires during cleaning of wheel wells.
11-Each part of steel , aluminum , or stainless steel subject to the hydrogen emrittlment process must be totally protected from the exposure.
12-Do not allow any agents to contact aircraft wiring .
13-Read the warnings and cautions labels on product containers carefully.
1-
Oxidation : it can be called the dry corrosion ,it happens when chemical reaction happens between the air and the metal surfuce it usually happens between the oxygen atoms in the air and the metal .
Uniform surface corrosion : its caused by reaction of metalic surfaces with atmospheric contaminants .
Pitting corrosion : pitting is likely result of uniform surface corrosion left untreated
. Galvanic Corrosion : this common type of corrosion occurs any time dissimilar metals makes elictrical contact in the presence of an electrolyte .
Concentration cell corrosion : is a corrosion of metals in a metal -to-metal joint .
Oxygen concentration cell corrosion : when water cover the aluminum surfaces and seeps through , it makes reaction with the air oxygen and it atracts the electrons and it turns the water to hydroxide which is corrosive .
Metal Ion concentration cell corrosion : Metals that depend on a tightly adhering passive film ( usually an oxide ) for corrosion protection ; can be corroded by active-passive cells The corrosive action usually starts as an oxygen concentration
cell corrosion.we can also say that Concentration cell corrosion occurs when two or more areas of a metal surface are in contact with different concentrations of the same solution . There are three general types of concentration .
Filiform corrosion is a special form of corrosion that occurs under some thin coatings in the form of randomly distributed threadlike filaments . Filiform corrosion is also known as Underfilm Corrosion or "filamentary corrosion". It occurs on metallic surfaces coated with a thin organic film that is typically 0 .1 mm thick. The pattern of attack is characterized by the appearance of fine filaments emanating from one or more sources in semi-random directions. The filaments are fine tunnels composed of corrosion products underneath the bulged and cracked coating . It can be visually recognized without using a microscopy . Filiform corrosion has been observed on surfaces of coated steel , magnesium , and aluminum with thin coatings of tin , silver , gold , phosphate , enamel , and lacquer . It has also been observed on paper-backed aluminum foil.
Intergranular corrosion is localized attack along the grain boundaries , or immediately adjacent to grain boundaries , while the bulk of the grains remain largely unaffected . This form of corrosion is usually associated with chemical segregation effects ( impurities have a tendency to be enriched at grain boundaries ) or specific phases precipitated on the grain boundaries . Such precipitation can produce zones of reduced corrosion resistance in the immediate vicinity .
Exfoliation: corrosion that proceeds laterally from the sites of initiation along planes parallel to the surface , generally at grain boundaries, forming corrosion products that force metal away from the body of the material . giving rise to a layered appearance.
Stress Corrosion: is evidenced when the metal strength loss resulting from the combined stress and corrosion is greater than the effects of stress and corrosion acting separately . The magnitude of the combined effect is a measure of the susceptibility of the material to stress corrosion . Stress corrosion is generally evidenced as cracks giving an appearance of brittleness in a material which is otherwise has normal ductile properties . The cracks may follow intergranular paths which grow at relatively slow velocities . If the load is constant during the period of crack growth the cracks will eventually reach a critical size to result in material failure.
Corrosion Removal
Before starting any corrosion removal , you must conduct an inspection and evaluation of the suspected area. When you inspect an aircraft or a particular area of an aircraft for corrosion , you should follow the steps listed below .
1 . Clean the area thoroughly .
2 . If an area is suspected of having corrosion , visually inspect the area by using a magnifying glass .
3 . To preclude metal damage , remove paint chemically from areas suspected of having underlying hidden corrosion . Use abrasive paint removal techniques only when corrosive products are observed .
4 . After removing the paint, use a magnifying glass to determine the extent of the damage , especially if there is evidence of corrosion on critical parts . Corrosion cracks must be detected as early as possible .
5 . Refer to the applicable structural repair manual ( SRM ) or MIM for damage limits . Metal loss damage is accumulative . When assessing corrosion damage , consider prior metal loss , including areas on the opposite side of the part . Propellers and helicopter blades have critical balance requirements . Refer to the propeller and blade manuals that apply for the evaluation and repair limits of corrosion , erosion , and abrasive damage . After the aircraft or aircraft part has been inspected , the extent of the corrosion damage must be correctly evaluated .
www.corrosionclinic.com
https://corrosion-doctors.org
https://www.roymech.co.uk
www.tpub.com